Clarification on code output

Hey everyone,


I've been experimenting with C programming and came across an interesting code snippet. I'm a bit confused about its behavior and was hoping you could help me out.

Code:

---

#include <stdio.h>


int main()


{


            int x;


            x = 10; 


            if(x > 10)


                        x -= 10;


            else if(x >= 0)


                        x += 00;


            else if(x)


                        x += 10;


            else


                        x -= 10;


            printf("%d\n",x);


            return 0;


}

---

The output of this code surprised me; it's giving 10 as the output, but I expected it to be 20.In the given code, we have an integer variable x initially set to 10. The program then goes through a series of conditional statements to modify the value of x. Let's break it down step by step:

if (x > 10) - This condition is not satisfied (10 is not greater than 10), so the program moves to the next condition.


else if (x >= 0) - This condition is satisfied (10 is greater than or equal to 0). However, the statement x += 0; does not change the value of x, so it remains 10.


else if (x) - This condition is also satisfied (10 is a non-zero value). The statement x += 10; modifies the value of x to 20.
else - This block is not executed since the previous conditions were satisfied.


As a result, the final value of x after these conditions is 20,

Can someone explain why the final value of x is 10 instead of what I anticipated?


Thanks in advance for your help!

there is a big difference between

Code:

---

if ( x == 1 )
  do something

if ( x == 2 )
  do something
if .......

---

and

Code:

---

if ( some condition )
  do something
else if (another condition )
    do something else
else if ........

else
  Default case

---

the first one is 3 separate if statements each one will be tested. the second one is one block only one condition will be executed

in your example the first condition that evaluates to true is as you say x >= 0 there for the next line is executed and zero is added to 10. That is then the end of the if block so the next line executed is your printf hence why the answer is 10 ( 10 + 0 )

Just run the code in a debugger, step through it line by line if you're confused.

Code:

---

$ gcc -g foo.c
$ gdb -q ./a.out
Reading symbols from ./a.out...
(gdb) b main
Breakpoint 1 at 0x1155: file foo.c, line 13.
(gdb) run
Starting program: ./a.out
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Breakpoint 1, main () at foo.c:13
13                    x = 10; 
(gdb) n
16                    if(x > 10)
(gdb)
22                    else if(x >= 0)
(gdb)
40                    printf("%d\n",x);
(gdb)
10
43                    return 0;
(gdb)

---

Quote:

---

Originally Posted by Salem

Just run the code in a debugger, step through it line by line if you're confused.

---

I don't have gdb but I am using printf statement for debugging

Code:

---



#include <stdio.h>


int main()
{
            int x;


            x = 10; 


            if(x > 10){
                x -= 10;
                                printf("True condition 1 x : %d\n", x);
                        }


            else if(x >= 0){
                x += 00;
                                printf("True condition2 x : %d \n", x);
                        }
            else if(x){ // x = 10 none zero I don't understand why it doesn't execute 
                x += 10;
                                printf("True condition3 x : %d \n", x);
                        }


            else{
                x -= 10;
                                printf("True condition4 x : %d \n", x);
                        }


            printf("final x : %d\n",x);


            return 0;


}

---

True condition2 x : 10
final x : 10

my only question

Code:

---

else if(x){ // x = 10 none zero I don't understand why it doesn't execute 
                x += 10;
                                printf("True condition3 x : %d \n", x);
                        }

---

because the condition above evaluates to true
so that condition isn't tested

Because a true condition was encountered , the subsequent else if and else conditions are skipped entirely